diff -ru menhir-20070322/infer.ml menhir-20070322.patched/infer.ml
--- menhir-20070322/infer.ml	2007-03-22 21:12:49.000000000 +0100
+++ menhir-20070322.patched/infer.ml	2007-05-14 18:07:02.000000000 +0200
@@ -332,9 +332,12 @@
   (* Invoke ocamlc to do type inference for us. *)
 
   let output =
+    let incl_dirs =
+      String.concat " " (List.map (fun s -> "-I " ^ s) Settings.incl_dirs)
+    in
     IO.winvoke
       [ write grammar ]
-      (Printf.sprintf "%s -c -i %s" Settings.ocamlc (Filename.quote mlname))
+      (Printf.sprintf "%s %s -c -i %s" Settings.ocamlc incl_dirs (Filename.quote mlname))
       [ remove mlname ]
   in
 
diff -ru menhir-20070322/settings.ml menhir-20070322.patched/settings.ml
--- menhir-20070322/settings.ml	2007-03-22 21:12:49.000000000 +0100
+++ menhir-20070322.patched/settings.ml	2007-05-14 18:50:58.000000000 +0200
@@ -93,6 +93,9 @@
 let ocamldep =
   ref "ocamldep"
 
+let incl_dirs =
+  ref []
+
 let logG, logA, logC =
   ref 0, ref 0, ref 0
 
@@ -131,6 +134,7 @@
   "--no-stdlib", Arg.Set no_stdlib, " Do not load the standard library";
   "--ocamlc", Arg.Set_string ocamlc, "<command> Specifies how ocamlc should be invoked";
   "--ocamldep", Arg.Set_string ocamldep, "<command> Specifies how ocamldep should be invoked";
+  "-I", Arg.String (fun s -> incl_dirs := s :: !incl_dirs), "<dir> Add <dir> to the list of include directories";
   "--only-preprocess", Arg.Set preprocess_only, " Print a simplified grammar and exit";
   "--only-tokens", Arg.Unit tokentypeonly, " Generate token type definition only, no code";
   "--raw-depend", Arg.Unit (fun () -> depend := OMRaw), " Invoke ocamldep and echo its raw output";
@@ -237,6 +241,9 @@
 let ocamldep =
   !ocamldep
 
+let incl_dirs =
+  !incl_dirs
+
 let logG, logA, logC =
   !logG, !logA, !logC
 
diff -ru menhir-20070322/settings.mli menhir-20070322.patched/settings.mli
--- menhir-20070322/settings.mli	2007-03-22 21:12:50.000000000 +0100
+++ menhir-20070322.patched/settings.mli	2007-05-14 18:05:47.000000000 +0200
@@ -97,6 +97,7 @@
 
 val ocamlc: string
 val ocamldep: string
+val incl_dirs: string list
 
 (* How verbose we should be. *)